1) Field of the Invention
This invention relates to a new transmission system employed for manual or automatically changing the gears in scooters, to enable the vehicle to be driven with different speeds and with varying load conditions. The invention is particularly concerned with a compact three-shaft system, designed to achieve required gear ratio steps in a positive and efficient manner.
2) Description of the Prior Art
Scooters are driven by prime movers like thermal engine working on fuels ie. gasoline, diesel, LPG or can be battery operated. Since the vehicle on road has to negotiate different gradients with varying load conditions and at different speeds, it is provided with either manual or automatic transmission. The present scooter with manual gear—shift transmission consists of gears in constants mesh, which are laid on two shafts, namely clutch shaft and the output shaft on which the rear wheel is mounted. The power flow from crank shaft to clutch shaft is transmitted through a primary gear reduction. In this known system, engine and transmission share the same lubricating oil in case of engines working on four-stroke principle. The shifting is done through cross selector mechanism operated by hand. In case of motor cycles a known two-shaft transmission system is used, namely clutch shaft and output shaft on which output sprocket is mounted and operated by foot. In order to have a 5-speed transmission, it is necessary to have 5 pairs of gears (10 gears) in constant mesh ie. each shaft having 5 gears.
A disadvantage of the present system is that the extreme angular travel of the twist grip in case of scooters is large and at the extreme position, operation of the control switches provided on left side of handle bar is difficult. The difficulty increases further when there is a need to adopt 5 speed gear transmission.
Yet another difficulty in the present system is that in the case of engines working on four stroke principle, same lubrication oil is used for lubricating transmission parts (shaft, clutch gears etc.) and engine parts (piston, camshaft, valves etc.) which is detrimental to the life of engine parts due to tiny wear particles generated in the transmission system.
Yet another disadvantage of conventional system for 4-stroke engine is that the clutch components are lubricated by engine oil which is relatively at higher temperature, which hinders proper functioning of clutch.
One of the object of the present invention is to provide an improved transmission system for the scooter, which is compact in nature and can be accommodated within the rear wheel rim diameter code.
Another object of the present invention is to provide an improved transmission system for scooter in which gear shifting can be achieved through a hand operated or foot operated control system or automatically ie. by, electrical motor, by solenoid actuated electrically/hydraulically/pneumatically.
Yet another object of this invention is to provide less angular travel of the twist grip (when shift mechanism is controlled by hand) with a resetting action easing gear shifting and operation of the control switches provided on left hand side of handle bar.
A still further object of the present invention is to use the same transmission system for different wheel sizes.
Still one more object of the present invention is to provide an improved transmission system for scooters, which can provide for use of separate lubrication oil for engine parts (piston, camshaft, valves etc.) and transmission parts (shaft, clutch gears etc.) for engines working on 4 stroke principle.